Butadiene dimerization



United States Patent BUTADIENE DIMERIZATION Anthony H. Gleason, Scotch Plains, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Nov. 26, 1958, Ser. No. 776,451

14 Claims. (Cl. 260-666) The present invention relates to the preparation of the dimer of butadiene-1,3, which polymer is 4-vinylcyclohexene-l. The invention relates particularly to an improved thermal process for the preparation of 4-vinylcyclohexene-l by polymerization of butadiene-L3 in the presence of an additive and if desired also a diluent, so as to prevent the formation of undesired high molecular weight oily polymers and also solid higher polymer gel deposits.

Ordinarily, in thermal butadiene dimerization processes high molecular weight oily polymers are formed in small quantities along with gel type polymers which tend to foul the reactor and transfer lines. These, of course, interfere with the formation of the desired dimer and also reduce the yield of product obtained. The so-called dimer is useful-as an intermediate in preparing aromatic compounds from aliphatic hydrocarbons as it can be readily dehydrogenated to an aromatic derivative and is also useful for other purposes.

It is the primary object of the present invention to provide a process whereby improved yields'of 4-vinylcyclohexene-l are obtained from butadiene-l,3 and in which problems of reactor-fouling due to gel-formations-are eliminated or are greatly reduced. This problem of gel formation is quite serious since the gel is of the popcorn" variety which tends to grow at an exponential rate once it is laid downon reactor or transfer linesurfaces. It thus can force frequent shutdown Oftheentire reactor unit. a

- According to the present invention, butadien'e is di-' merized at temperatures between 130 and 160 C., pref+ erably 140-160 =C., e.g. 160 C. under high average pressures of 400-1200 p.s.i.g.v preferably of about .500- 600 p.s.i.g., e.g. 550 p.s.i.g., using rather small quantities given the time required for dimerization decreases as temperatures and pressures increase; Selectivity of con- "ice 20 hours,e.g. 16 hours. Of course, within the ranges version to the desired 4-vinylcyclohexene-1 is'greater than 95% and conversions of butadiene of above 90% are 'obtained at temperatures in the range of 1.40-160 F. using. reaction times of above 16 hours. Of course, in the operation of the process it may be desiredto react the butadiene for a shorter time to obtain a smaller conversion and recycle product or to separateunreacted butadione from the product and recycle said butadiene. In: all

- instances, of course, it is desirable to use as the diluent a material such as the dimer itself or a material which is readily separable from the dimer product, ,If the process is operated so as to: obtain low conversiongadditionally the diluent should be readily separable from butadiene.

High pressures, e.g. of the order of 400-1200 p.s.i.g., are employed in the process. Lower pressures are used where larger amounts of diluent are used. Higher temperatures, preferably those up to and not higher than the critical temperature ofthe butadiene (163 Ck); also in the order of l-5ywt. percent, preferably 2-4 wt. peramines may have from 48 carbon atoms, and the alkyl.

groups may be the same or mixed. The diluent may be any of the well known aromatic solvents, preferably benzene homologs such as benzene or toluene; chlorinated paratfins such as ethylene dichloride; and the substantially peroxide free dimer itself. The dimer, 4-vinylcyclohexane-1 is subject to the formation of peroxidev upon standing in air and these peroxides promote the formation of gel and higher polymer. It is therefore necessary to exclude air from the dimer if it is stored, before recycling or alternatively the dimer'may be treated with sodium to remove these peroxides. The diluent is used in amounts of 20-50 wt. percent, based on the total feed, preferably 25-35 wt. percent, e.g. 30 wt. percent.

provide accelerated reaction times.

Although it is knowntha't antioxidants will reduce gel and oily polymer formation to' a limited extent, it is also known that they will not eliminate the formation of these higher polymers completely at the temperatures found suitable for a reasonable rate of dimerization (130-160,

C.). Likewise, it is known that soluble copper salts such as copper naphthenate, act as strong inhibitors of higher polymer formation but only in the temperature range of l00-l20 0., which is too low for practical reaction rates. r

I Data has now been obtained in batch laboratory operations, that will be hereinunder described, which indicate that if l-5 Wt. percent of aqueous-solutions of ammonia or of dialkylamines are added to the butadiene, in the presence :of 20-'50 percent, preferably 125-35 wt. percent based on total feed of a diluent, gel formation is completely eliminatedfiand .oilyliquid polymer formation is reduced to only about 2% of the buta'diene' charge; Ifaqueous ammonia is used it is preferred to use conf centrated 28% ammonia. However, it iscontemplated that larger amounts of a more dilute ammoniamay also be used.. 1

The following experiments, reported in the table below, were'all obtained in a laboratory 3 /2 liter, stainless steel bomb filledto about 2 liters with liquid. butadiene, additive (and diluent if any) at 0 C; The bomb was then sealed and thetemperature was raised to the desired levels reported in the chart, pressures increasing autogenously. For example, where no diluent or additive was used, the maximum pressure rose to 1000 p.s.i. upon heating to 125 C., then dropped to 500 p.s.i..after about two hours, and at the end of the run after cooling to 25 C. the pressure was negligible. In all the following runs, conversions of butadiene were above wt. percent except where temperatures of 120 and. F. were used (marked with an asterisk), in which cases only 75% by weight conversion and 55% by weight conversion were iobtained, respectively in the specified times. Where a noticeable precipitation. of gel was obtained in the no gel was noticeable this was reported as Butadzene dlmerzzatzon runs Percent Additive, wt. percent Diluent, wt. percent of Temp., Time. Gel by wt. on H Total Feed 0. Hours Higher Polymers None 16 6. 5 Hydroqulnone 0 2 18 5. 7 a naphthol 0.2.- 40 Cu naph. 1.0-. 20 10 Cu naph. 2.0 20 5. 4 Cu uaph. 3.0 65 9 Cu naph. 3.0 20 6.3 Cu mph. 1.6 65 1.4 Cu naph. 2.0-. 65 0 aq. N aOH 24 6 Fe naph. 1.0 24 Pb naph. 1. 24 Aniline 4... aq. NH: 2 1s n: naphthol 1.0 1s 13 Benzoyl Perox. 0.7"--. 20 10. 0 None dimer t)(with sodium 160 20 4.5

1e 17 20 1s 20 3.7 11 2.1 21 6.6 17 4. 5 1.5 18 .3 18 i 11.1 18 1s 160 is 3 methyl pentane 160 18 Do. ethyl ether 30 160 18 Do. 18 Do- 25 9 Do. 16 13.5 no. NH1 a... benzene so 160 17 g: aq. NH; 3 do 160 17 dlethyl amine 1.8- do 160 21 It should be noted that in all cases but one where the 7. The process of claim 1 in which the additive is condimer was used as the diluent, poor results were obtamed. centrated aqueous ammonia. This was due, at least in part, to the fact that the dimer 8. The process of thermally dimerizing butad1ene-1,3 used had been exposed to the air for a conslderable to produce 4-v1nylcyclohexene-1 which comprises mamperiod and this needed a sodium treatment to remove the peroxides formed. These peroxides, of course, catalyze the formation of higher polymers. In commercial operations such a treatment to remove peroxides would not be required since the polymer need not be exposed to the am What is claimed is: r

l. The process of thermally dimerizing butadiene-l,3 to produce 4-vinylcyclohexene-l which comprises maintaining the hutadiene at a temperature of 130 to 160 C. in the presence of 1-5 wt. percent based on butadiene of an additive selected from the group consisting of aqueous ammonia and dialkyl amines and 20-50 wt. percent based on feed of a diluent selected from the group consisting of peroxide free butadiene dimer, benzene and benzene homologs and chlorinated parafiins to obtain a substantial yield of the dimer.

2. The process of claim 1 in which temperatures are maintained in the range of 140-160 C.

3. The process of claim 1 in which thefeed materials are held at conversion temperatures for 8 to 25 hours.

4. The process of claim 1 in which the feed materials are held at conversion temperature for 15 to 20 hours and in which at least 90% conversion of butadiene is obtained.

5. The process of claim 1 in which the diluent is benzene.

6. The process of claim 1 in which the diluent is the dimer, 4-vinylcyclohexene-l.

taining the butadiene at a temperature of to 160 C. in the presence of 24 wt. percent based on butadiene of an additive selected from the group consisting of aqueous ammonia and dialkyl amines and 25-35 wt. percent based on feed of a diluent selected from the group consisting of peroxide free butadiene dimer, benzene and benzene homologs, and chlorinated parafiins to obtain a substantial yield of the dimer.

9. The process of claim 8 in which temperatures are maintained in the range of -l60 C.

10. The process of claim 8 in which the feed materials are held at conversion temperatures for 8 to 25 hours.

11. The process of claim 8 in which the feed materials are held at conversion temperature for 15 to 20 hours and in which at least 90% conversion of butadiene is obtained.

12. The process of claim 8 in which the diluent is benzene.

13. The process of claim 8 in which the diluent is the dimer, 4-v'mylclohexene-l. 14. The process of claim 8 in which the additive is concentrated aqueous ammonia.

References Cited in the file of this patent UNITED STATES PATENTS 2,401,414 Doumani et al June 4, 1946 2,438,041 Dutcher Mar. 16, 1948 2,867,672 Hemmerich Jan. 6, 1959 

1. THE PROCESS OF THERMALLY DIMERIZING BUTADIENE-1,3 TO PRODUCE 4-VINYLCYCLOHEXENE-1 WHICH COMPRISES MAINTAINING THE BUTADIENE AT A TEMPERATURE OF 130 TO 160*C. IN THE PRESENCE OF 1-5 WT. PERCENT BASED ON BUTADIENE OF AN ADDITIVE SELECTED FROM THE GROUP CONSISTING OF AQUEOUS AMMONIA AND DIALKYL AMINES AND 20-50 WT. PERCENT BASED ON FEED OF A DILUENT SELECTED FROM THE GROUP CONSISTING OF PEROXIDE FREE BUTADIENE DIMER, BENZENE AND BENZENE HOMOLOGS AND CHLORINATED PARAFFINS TO OBTAIN A SUBSTANTIAL YIELD OF THE DIMER. 